Polymers

Needs no petrochemistry at all. If rubber trees grow near you, this is a very high priority.

1. Tap the latex, and coagulate it with dilute acetic or formic acid.
2. Roll into sheets, wash, and dry or smoke them.
3. Mix with sulphur — a few parts per hundred of rubber for soft rubber, up to 30–50 parts for hard ebonite — plus zinc oxide as an activator.
4. Cure with heat, roughly 140–160 °C, for tens of minutes, in a mould for gaskets and seals.

Under-cured rubber is sticky; over-cured is brittle. Test by stretching.

A genuinely simple hard plastic makeable at small scale, good for buttons, handles and fittings.

Warm skimmed milk, add vinegar — the protein, casein, separates as curd. Wash, press and dry it, then shape it. For a durable, water-resistant plastic, harden it by soaking in formaldehyde solution for days to weeks depending on thickness.

Formaldehyde is a carcinogen and a strong irritant: work with ventilation, gloves and eye protection, and keep it covered.

Phenol — from coal tar — reacted with formaldehyde gives a resin that, mixed with a filler such as wood flour and pressed in a heated mould at around 150–180 °C, sets permanently into a hard, heat-resistant thermoset: Bakelite.

It is a superb electrical insulator — the enabling material for early electrical equipment. Phenol absorbs through skin and burns it, and is toxic: gloves, eye protection, ventilation.

Celluloid and other nitrocellulose plastics are dangerously flammable — nitrocellulose is chemically close to guncotton — and stores of celluloid film and goods caused catastrophic fires, including cinema and warehouse fires with heavy loss of life.

For transparent film and sheet, prefer cellulose acetate or later petrochemical polymers. If nitrocellulose is used at all, store only small quantities, cool, separated from heat and flame, and never in bulk.

Polyethylene, PVC, polystyrene and nylon need cracking, catalysis, gas separation and continuous process control at a scale that implies a real chemical industry — refinery feedstock, high-pressure or catalytic reactors, and large, steady power.

They are not a workshop project. Start with the natural and simple polymers above, and reach for petrochemicals when a refinery and a chemical plant already run reliably. Salvaged plastics — melted, remoulded or reused — bridge the gap.

The first time round, this step produced a material that persists for centuries in every ecosystem on earth. You already know that.

• Durable goods over disposable ones — a reusable container rather than a thousand single-use ones.
• Mark every part with its polymer type, so it can be sorted and recycled.
• Favour materials you can reuse, regrind or burn cleanly.
• No single-use plastic where a durable alternative exists, set in published rule.

See Futures.

You have knowledge the first industrialists did not. Skipping these costs almost nothing:

• PCBs — electrical insulating oils that persist and poison.
• Asbestos — fibres that cause mesothelioma decades later.
• Lead stabilisers and pigments.
• Persistent fluorinated chemicals — non-stick and water-repellent coatings that never break down.

Write the refused list into the code and check every new material against it. See decide what not to rebuild.